WASHINGTON (CNN) -- President Bush said Thursday he "answered every question" posed to him by the 9/11 commission during what was described as an extraordinary session at the White House with the panel investigating the September 11, 2001, terrorist attacks.

"It was wide-ranging, it was important, it was just a good discussion," Bush told reporters in the White House Rose Garden, shortly after the closed-door session ended.

The entire 10-member bipartisan commission -- known formally as the National Commission on Terrorist Attacks Upon the United States -- attended the meeting in the Oval Office.

Bush and Vice President Dick Cheney answered questions from the commissioners for more than three hours.

The president dismissed suggestions that he appeared before the panel with Cheney to coordinate stories.

"If we had something to hide, we wouldn't have met with them in the first place," Bush said. "We answered all their questions."

Bush said it was important for him and Cheney to appear together so that commission members could "see our body language... how we work together."

Bush described the session as "cordial," but declined to provide any details about topics discussed. He said he was never advised by White House Counsel Alberto Gonzales -- who attended the session, along with two members of his staff -- not to answer a question.

'We are vulnerable'

Bush stressed that the United States remains vulnerable to terrorist attacks.

"So long as there's an al Qaeda enemy that's willing to kill, we are vulnerable," Bush said.

A statement from the 9/11 commission described the meeting as "extraordinary" and thanked the two men for their cooperation.

"The commission found the president and the vice president forthcoming and candid," the statement said. "The information they provided will be of great assistance to the commission as it completes its final report."

Commission member Tim Roemer, a Democrat and former congressman from Indiana, said Bush was "very direct" in his answers.

"He was cooperative, he was frank, he was gracious with his time," Roemer told CNN.

The commission is investigating what has become the defining moment of the Bush presidency -- the worst terrorist attacks on U.S. soil, carried out by 19 hijackers who commandeered four U.S. commercial jets.

Two of those jets slammed into New York's World Trade Center, causing the towers to collapse, a third jet crashed into the Pentagon, and the fourth slammed into a field in western Pennsylvania. About 3,000 people were killed.

The commission is charged with coming up with an authoritative account of the attacks, including any intelligence and security lapses. The commission will also draft recommendations on how to safeguard against possible future attacks.

It is rare for a sitting president to talk to such a panel. There have been only a handful of appearances since 1862, when President Lincoln discussed relieving a Civil War general.

Bush had only positive words for the session.

"They had a lot of questions and ... I'm glad I did it," Bush said. "I'm glad I took the time."

But the administration initially opposed the creation of the commission. The White House relented amid pressure from some 9/11 family members and it later backed down from its opposition to an extension of time for the commission.

The commission now has until July 26 to finalize its report, but that report may not be released publicly at that time, pending a security review by the White House.

No transcript

Bush and Cheney did not testify before the panel -- they were not under oath and there was to be no recording made of the session nor a stenographer in the room.

The two members of the White House counsel's staff were expected to take notes during the session, and the commission members were also allowed to take handwritten notes.

Bush brushed off a question from a reporter Thursday on whether 9/11 families were entitled to a transcript of the session.

He did not repeat the answer, but the White House has said there will not be a transcript of the session. Bush said he expects details of his "conversation" with the commission to go into its final report.

The Oval Office session began at 9:30 a.m. and ended at 12:40 p.m., although two commission members -- Lee Hamilton, the vice chairman, and Bob Kerrey -- left about an hour earlier.

In a written statement, Kerrey said he left early to attend "a previously scheduled meeting with Senator Pete Domenici on Capitol Hill."

Former President Clinton and former Vice President Al Gore have also met with the commission. Their sessions were also private and, like Bush and Cheney, they were not under oath. However, Clinton and Gore appeared separately before the panel, and their sessions were recorded.

Bush and Cheney had spent several hours over the past few days preparing, aides said.

Bush, for example, reviewed intelligence briefings from 2001 and spent time talking to Gonzales, national security adviser Condoleezza Rice and chief of staff Andrew Card, who was traveling with Bush in Florida on the morning of the September 11, 2001, attacks. (Rice delivers tough defense of administration)

A senior administration official said Bush's preparations also included conversations with Cheney.

Officials said that among the documents prepared for both men to review were intelligence reports from the months and weeks before the attacks and what one senior official called "chronologies and other records of events in that time period."

They also reviewed transcripts and summaries of previous testimony to the commission -- including that of former White House counterterrorism chief Richard Clarke, officials said.

Clarke was critical of the Bush administration in his testimony before the commission, saying it considered terrorism "important" but not "urgent" before the 9/11 attacks. (Clarke vs. Rice: Excerpts from testimony)

The commission recently held a series of public hearings, during which some witnesses faulted Bush's anti-terrorism policies before the 9/11 attacks. And statements prepared by the commission staff have faulted the FBI and CIA for their policies and lack of cooperation before that time. (9/11 commission faults U.S. intelligence)

The Justice Department has also released documents on its Web site about Jamie Gorelick -- a Democratic member of the commission who served in the Justice Department under President Clinton -- and her role in developing a legal "wall" on the sharing of intelligence information.

Some witnesses who appeared before the 9/11 commission said bureaucratic hurdles impeded the effort to thwart terrorism.

That wall was initially affirmed by Justice Department under Bush, but the restriction on sharing intelligence information was lifted as part of the post-9/11 Patriot Act.

At the White House, spokesman Scott McClellan said Bush was "disappointed" by the release of the documents.

"That's what the Justice Department did; we were not involved in it," McClellan said. He added that Bush expressed his disappointment to the commission.

"The president does not believe we ought to be pointing finger during this time period," McClellan said.